The present invention relates to the treatment of an effluent from a substrate processing chamber.
In a substrate processing chamber, electronic circuits and displays are fabricated on substrates such as semiconductor wafers and glass. In such chambers, semiconductor, dielectric, and conductor materials, are formed on the substrate by chemical vapor deposition (CVD), physical vapor deposition (PVD), oxidation, nitridation, ion implantation and etching processes. In CVD processes, a reactive gas is used to deposit material on the substrate. In PVD processes, a target is sputtered to sputter deposit material on the substrate. In oxidation and nitridation processes, an oxide or nitride material is formed on the substrate by exposing the substrate to a suitable gaseous environment. In ion implantation, ions are implanted into the substrate. In subsequent etching processes, etch-resistant features comprising resist or hard-mask, are formed on the substrate and the exposed portions of the substrate between the etch-resistant features (substrate open area) are etched to form patterns of gates, vias, contact holes or interconnect lines. Chamber cleaning processes may also be used to clean the chamber in-between processing of batches of substrates. These processes are often performed with energized gases, such as for example, RF (radio frequency) plasmas, LF (low frequency) plasmas, and microwave activated gases, but may also be performed with suitable non-energized gas compositions. They are also often performed at low or sub-atmospheric pressures.
The effluent generated in these processes can often contain different compositions of flammable and/or corrosive gases, sub-micron sized process residue particulates and gas phase nucleated materials, and other hazardous or environmentally polluting compounds. For example, the effluent may contain different compositions of halogen containing gases, perfluorocompounds (PFCs), chlorfluorocompounds (CFCs), hazardous air products (HAPs), and volatile organic compounds (VOCs). The effluent gases can contain un-reacted or excess portions of the process gas used for processing the substrate or cleaning the chamber, as well as reaction byproducts that arise from reactions between dissociated and ionized species formed in the energized gas in the chamber. In one version of an etching process to etch layers of silicon dioxide, the effluent can contain etchant gases such as fluoride and other halogen containing gases and PFCs, along with silicon-containing particulates that are formed during processing. Chamber cleaning processes that use fluorinated gases, such as F2, CF4, NF3, C3F8, and C4F8O and other fluorine-containing gases to clean process residues from the chamber walls, can also exhaust effluent containing various combinations and formulations of fluorinated gases, PFCs, and residue particulates. Also, in the deposition of dielectrics, such as silicon dioxide, or low K dielectrics such as silicon oxycarbide, an excess of a silicon-containing gas, such as for example, trimethylsilane gas, is used to generate the desired deposition on the substrate and as much as about 60% of the trimethylsilane introduce in the chamber can end up in the effluent stream.
The effluent can be treated in an effluent treatment reactor, such as for example an effluent combustion chamber, to reduce the emissions of the hazardous and pollutant gases into the environment. However, it is difficult to treat different compositions of effluents to reduce, for example, their PFC content to a desirably low level without other adverse effects, such as for example, simultaneously causing excessive erosion of the internal walls and surfaces of the effluent chamber. For example, chamber surfaces made from aluminum can be easily eroded by chlorine or fluorine containing gases, such as for example, HF and NF3. The erosive effect of the effluent can be especially strong at the high temperatures needed to treat the effluent in combustion reactors.
Another problem arises when residue and particulate materials are present in the effluent. Such particulates are often sub-micron sized and they can accumulate in and clog up the pipes and apertures of the effluent treatment reactor. A conventional filter placed in the effluent path can filter out such particulates. However, the filter may also impede the flow rate of effluent through the exhaust causing a back-pressure to develop in the processing chamber. The back-pressure is undesirable because it can increase the low or sub-atmospheric operating pressure maintained in the processing chamber.
Accordingly, it is desirable to have an effluent treatment system capable of effectively treating different compositions of effluent to control their emissions and minimize the release of hazardous or pollutant gases into the environment. It is also desirable to remove particulates present in the effluent during treatment of the effluent without causing excessive back-pressure of effluent gases into the chamber. It is further desirable to have an effluent treatment reactor capable of withstanding erosion and corrosion from the halogenated gases and byproducts of the effluent.